Scuplting numbers onto a 12 sided die.
Select the mesh and go into edit mode (TAB to toggle).

Switch you selection mode to face (Ctrl+TAB >> F).

Select which face you desire to work on.

Set your view normal to that surface (Shift+Numpad 7).

Use Alt+Spacebar >> V to switch your manipulator so that it oriented to your view.

Select a vertex on that face and Shift+S >> U to set your cursor to the active selection.

Go back into Object Mode (TAB to toggle).

Ensure that the toolshelf at the left side of the screen is visible by ensuring that your mouse is hovering over the 3D view, then hit T.

Add a Text object by using Shift+A >> T.

Immediately look at the toolshelf toward the bottom half of the shelf, and check the Align to View checkbox.

Now scale, rotate and drag your text to where you want it in the views XY plane.

You can Then manipulate your text's extrusion, convert it to a mesh, and boolean difference it from your mesh like in this post.

Then just repeat this for every side.

You can see a quick .gif animation of this process at the following link